Oscillation generator



y 23, 1929- .J. A. MILLER i,7l4,6&9

OSCILLATION GENERATOR Filed March 31, 1926' NVE N TO R James 4. M7/er BY W Hi5 ATTORNEY structure.

Patented May 28, 1929.

JAMES A. MILLER, OF SAN JOSE, CAHFORNIA, ASSIGNOR 0F ONE-FOURTH T0 JOHN FLAM, 0F .LOS ANGELES, ELLIOTT, 0F PALO ALTO, CALIFORNIA.

CALIFORNIA, AND THBEE-EIGHTHS TO OSCILLA'IION GENETOB.

Application filed March.- 31, 1926. Serial No. 98,834.

In the field of communication by the aid of radio, it is necessary to generate electrical currents of radio frequency, in order to make it possible to transmit the radiosignals. At the present time, it is common to utilize for this purpose, vacuum tube devices or arcs. These, by careful adjustment are capable of satisfactory operation to provide carrier frequency currents that may be modulated in any well-known way to produce either telegraphic signals or speech or music.

Nevertheless, both these devices have inherent limitations and disadvantages, which it is my purpose to overcome by the aid of the present invention.

In the case of the vacuum tube, the construction is delicate, and it has a limited life. Furthermore, for large output, the cost is very high. All of these disadvantages are obviated in my new type of oscillator.

As regards the Poulsen are, it is not only expensive, but requires frequent and constant attention and adjustment, for it is inherently an unstable apparatus. Furthermore, the frequency ran e is limited, for such an arc cannot reach the higher frequencies now in use. My new form of oscillator is very stable. It operates for hours without adjustment.

The fundamental characteristics of my invention may best be explained by comparing I it with the vacuum tube and the Poulsen arc, from which it differs both in theory and In the vacuum tube, use is made of the flow of electrons between electrodes, which are inclosed in a vessel exhausted to substantially a perfect vacuum. The electron discharge between electrodes is short and direct; there is no opportunity nor the means for producin additional electrons by collision of ions, w ich are mainly absent. In the Poulsen arc (or for that matter, the Hewitt or Vreeland mercury arc), there is a concentrated ionized discharge between electrodes, the concentrated discharge being merely another appellation for an arc. This discharge .depends upon conduction effects produced by the presence of ionized vapors. In both the arc and the vacuum tube, there is this much in common, that electrons are discharged from one electrode and received on another.

To this extent, my oscillator resembles both these old forms, for an electronicdischarge is secured between a cathode and an anode. But the discharge, although occurring in a gaseous atmosphere, is not an arc discharge, but instead a difiused gaseous discharge. Such a phenomenon I am enabled to obtain by the aid of apparatus to be hereinafter described. I have found its advantages to be important, and they include such factors as highly increased stability. There are furthermore, no moving parts, for it is unessential to rotate the electrodes, as in the Poulsen arc. In order to obtain the difi'used discharge, certain kinds of gas have been found by experiment to support such a discharge. F or example, such solid substances as carbon, SlllCOIl, or thorium have been found to combine with hydrogen in which the electrodes are enclosed, to form a hydride that assists in the formation of the glow discharge. lVithout the presence of some such solid, the device will not oscillate.

It is thus apparent that the characteristics of the device are substantially distinct from those of an ordinary concentrated discharge or are. Another distinction resides in the mode of using a magnetic field. In the Poulsen arc, the field is used to extinguish the arc, and 1s transverse to the direction of the arc.

of diffusing the discharge, and to increase the electron path, and is axial with respect to the electrodes. The difiusion I believe is useful n causing frequent collisions of the conducting ions in the stream, whereby the number of electrons therein is thus increased.

My invention possesses many other advantages, and has other objects which may be made more easily apparent from a consideration of one embodiment of my invention. For this purpose I have shown a form in the drawings accompanying and forming part of the present specification. I shall now proceed to describe this. form in detail, which illustrates the general principles of my invention; butit is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of my invention with a thin projecting edge 2 at its active extremity, forming an enlarged disc. Adjacent this disc is a cathode *1, having a large surface parallelling the surface at the end of anode 2. Under proper conditions, a glowing gaseous discharge 26, capable of sustained oscillations, exists in the form of an annulus between the edge 2 and the cathode 1. Such a discharge is stable and can operate for a long period without attention.

In order to secure this result, the discharge must be supported by an ionized vapor stream between the electrodes. Thus an enclosing chamber 21 is provided for the electrodes, which chamber can be formed by an insulation plate 17 through which the electrode 2 projects, as well as by a ring 25 separated by a gasket 23 from the plate 17 and serving to space this plate from a lower ring 6. A gasket 29 is interposed between rings 6 and 25. The anode 2 passes through ring 6 with a large clearance,and into a space formed between this ring and the cathode block 24 fastened in this instance below the ring 6. This cathode block and the ring 6 have a gasket 30 interposed between them, whereby the chamber 21 can be maintained gas tight. A gas inlet 20 passes through ring 25, through which a proper gaseous atmosphere can be introduced into chamber 21. Any convenient means can be used to seal this outlet, once the gas is introduced.

I preferably use hydrogen for the gas, at low pressure, of the neighborhood of atmospheric pressure, and I use for the cathode 1 a conducting material such as copper, preferably combined with some material, such as carbon, silicon, or thorium orother members of the same periodic group, or an alloy thereof, which is capable of combining withhydro gen and of forming an ionized gas. Upon between electrodes 1 and 2, a glowing dis charge is produced between them. The discharge may be started either by sticking the electrodes together or by inducing a high potential between them. The device normally operates at a nominal potential, such as 100-1000 volts, but severa times this may be required to give initial ionization to start operation. Of course the solid material (carbon, silicon, or thorium), can be introduced in other ways also, so long as an opportunity is given it of combining to form a hydride.

In order to ensure the spreading of the discharge 26, so as to encompass the entire disc 2 an axial magnetic field is provided. For this purpose, ring 6 is made from magnetic material and forms a magnet counterpoise for the direct current magnet core 5 located below the cathode block 24. By proper proportioning of the aperture in ring 6, as compared with the diameter of the disc 2 the path of the magnetic lines of force can be made such as to have a spreading action suflicient potential difference being applied on the discharge 26. A shell 7 of magnetic material not only serves to complete the magnetic circuit, but also to accommodate the core 5 and its energizing winding 11.

It is to be noted that the magnetic lines of force ass in a direction substantially axial or para lel with the direction of the electrodes. Its purpose is to spread the discharge 26 so as to give more opportunity for producmg ionization by collision and to prevent any concentrated, arc discharge.

In order further to assist in the prevention of any discharge that would in any manner resemble an arc, I arrange to keep both electrodes cool by the circulation of a cooling medium such as water, past the electrodes. For example, a water jacket 3 is formed between the bottom wall of the cathode block 2 1 and the bottom of the disc-like cathode 1, which rests upon a tight gasket 28. Tubes 9 connect to the space 3 and serve to carry cooling fluid to and from the cathode 1. In

a similar manner, anode 2 is supported in an anode head block 15, as by the aid of screw threads; it is hollow, and connects with an aperture in head 15, having a right angled extension 32 in which a cooling tube 10 is accommodated. Another tube 33 extends almost to the bottom of anode 2, and into the cooling chamber 4; it likewise connects with an aperture in head block 15, in which another cooling tube 10 is fastened. A gasket 31 is interposed between the top of anode 2 and the edge of the threaded aperture in which it is accommodated, for the purpose of securing a fluid tight connection. The circulation of water or other liquid in anode 2 can easily be traced by the aid of the arrows, from left hand pipe 10, through pipe 32, up in annular chamber 4, and out through right hand pipe 10.

It is to be noted that the cathode 1 has a large active surface, as compared with the anode 2. This is of importance to assist in keeping the discharge diffused, by actual trial probably this is due to the fact that substantially uniform impedance is offered to the discharge from all points on the periphery of the rim 2 to the cathode 1; and no sharp opposed edges are present between the two electrodes.

It is of course desirable, if not in fact indispensable, to provide for relative axial adjustment of the electrodes 1 and 2. For this purpose, anode 2 is slidably accommodated in a guide 22 fastened to the top of insulating plate 17, there being a gasket 32 interposed between the guide flange and the disc 17 A compression spring 16 is used to urge anode 2 resiliently away from cathode 1, and for this purpose it surrounds the anode and extends between the to of guide 22 and the bottom of block 15. 11 order to depress the anode 2 against the force of the spring 16, and to adjustits position thereby, a thumb screw 12 is provided, bearing against an insulation spacer 14 fastened to the top of block 15. A bracket 13 serves conveniently as a support for the screw 12, which is threaded therein. I r '1 In order to provide for electrical connections, a binding post 18 is provided onthe anode head block 15, and a similar post 19 is provided on the magnetic ring 6, which is in electrical contact with the cathode 1.

The manner in which the oscillator can be used is illustrated in Fig. 2, which represents a transmitting system for radio communica-, tion. A source 34, preferably of direct current is connected across the electrodes 1 and 2, and the magnetizing winding 11 is included in this direct current circuit. The oscillation circuit connects across the electrodes 1 and 2, and may include a Variable condenser 35 and the primary 36 of a transformer 37. This transformer has a magnetic core of fine laminations. Its secondary 38 may be connected with radiating apparatus, such as antenna 39, and ground 40. A loading inductance 41 may also be included in this circuit.

By varying the condenser 35, it is possible to vary the peak voltage across the electrodes and thus to adjust the speed of electronic flow to the frequency of oscillation, without materially affecting other characteristics of the system. This is due to several factors, now to be explained. Since the transformer 37 is a closely coupled one, the capacit of condenser 35 is the largest factor in t e impedance of the circuit, and when this capacity is reduced, the voltage across it is increased, and therefore also across the electrodes. This increase in electrode voltage causes the electrons or ions to travel faster between the electrodes, corresponding to a higher frequency. Since there is no necessity for increasing the gap between the electrodes, due to the gaseous character of the discharge, the load characteristic is left unaltered.

The construction and operation of In device are apparent from the foregoing. dis charge in the form of an annular glow exists between the electrodes, and is stable without attention or adjustment. There is no great waste from heating, and there are no moving parts, and it is possible to adjust the frequency between wide limits.

I claim:

1. In an oscillator, an anode and a cathode, one of said electrodes having a projecting peripheral edge adjacent its operating end, and the other having a cooperating surface spaced from the said end, and means whereby the electrodes are enclosed in a gaseous atmos-- phere capable of supporting a diffused oscillatory ionized discharge between substantially the entire periphery of said'edge and the adjacent electrode. v

2. In an oscillator, a pair of electrodes having cooperatingsurfaces between which a discharge can take place, the active surface of one of said electrodes being in the form of an annular edge around the electrode, and the active surfaceof the other electrode having an extent sufficient to provide substantially a plane area substantially perpendicular to the axis of said edge, and means for providing a hydride atmosphere for the discharge, said hydride being a compound of one of the elements in the carbon periodic group, whereby a stable diffused gaseous discharge is obtained between the electrodes.

3. In an oscillator, a pair of electrodes, and means forming a chamber in which the electrodes can be enclosed in a gaseous atmosphere in which hydrogen is present, one at least of the electrodes including in its structure, an element of the carbon periodic group, whereby a hydride of said element is formed as an ionized gas between the electrodes, and one of said electrodes having an active peripheral edge, and the other electrode having I a plane surface opposed to said edge an parallel thereto.

4. In an oscillator, a pair of electrodes, means for so cooling said electrodes as to prevent a concentrated or are discharge, and means whereby a diifused gaseous discharge of a compound of carbon and hydrogen is produced between the electrodes.

5. In an oscillator, a pair of electrodes, one of said electrodes having an active peripheral edge for supporting a discharge to an active surface on the other electrode, means forming an enclosing chamber for said electrodes, and means for passin a magnetic field through the space in a direction substantially axial with respect to the electrodes, whereby a concentrated or are discharge between the electrodes is hindered.

6. In a difiused gaseous dischargeoscil lator, a pair of electrodes, one of said electrodes having an active peripheral edge for supporting a discharge to an active-surface on the other electrode, means forming an en-' closing chamber for said electrodes, and means for hindering the formation of a con-' centrated or are discharge between the electrodes, comprising means for cooling the electrodes, and means for producing a magnetic field substantially axial with respect to the electrodes.

7. In an oscillator, a pair of electrodes, and means whereby a gaseous difiuscd discharge of oscillatory character is produced between the electrodes, comprising means for producing a gaseous conducting medium formed of a hydride of an element of the carbon periodic group, means for cooling both electrodes below the minimum temperature to support an arc, and means producing a magnetic field substantially axial with'respect to the electrodes.

8. In an oscillator, means for producinga closely coupled transformer fed by diffused gaseous oscillatory discharge, 3

sm means, an oscillatory load circuit fed by the transformer, said circuit determining the fre quency of operation, and a variable condenser in circuit with the means and the transformer primary.

9. In an oscillator, means for producing a gaseous diffused discharge of oscillatory character, comprising an anode and a cathode, said anode having a peripheral edge adjacent its operating end and active substantially entirely around its periphery, and said cathode having an opposed surface paralleling the active surface of the anode and of materially larger extent than said active surface, and means forming an enclosing chamber for said electrodes.

10. An oscillator characterized by the fact that electrodes are provided which are enclosed in an atmosphere of hydrogen combined with an element of the carbon, silicon, selenium, thorium group, and that means are provided to prevent a concentrated, are discharge between the electrodes.

11. In an oscillator, a cathode having substantially a plane active surface, an anode having a peripheral edge disposed so that spaced therefrom, and means insuring a discharge between said plane surface and substantially the entire periphery, comprising means for cooling the electrodes below the minimum tem erature requiredto support a concentrated ischarge, and means for producing a magnetic field substantially axial with respect to the active electrode surfaces.

13. In an oscillator, a pair of electrodes, means for preventing a concentrated are discharge between the electrodes, and means for producing a magnetic field substantially axial with respect to the electrodes, for increasing the ionic path between the two electrodes.

In testimony whereof I have hereunto set my hand.

JAMES A. MILLER. 

